Pneumatic tube systems



H. MACH ET AL PNEUMATIC TUBE SYSTEMS Aug. 9, 1966 2 Sheets-Sheet 2 Filed May 26, 1964 PRESSURE was 45m: 7- j I I I l I I I I I I I I I I I I I I I I I I I M cm I R A, T m m mm P v.

United States Patent 3,265,324 PNEUMATIC TUBE SYSTEMS Horst Mach and Hans-Joachim Peter, Berlin, Germany,

assignors to International Standard Electric Corporation, New York, N.Y., a corporation of Delaware Filed May 26, 1964, Ser. No. 370,303 Claims priority, application Germany, May 30, 1963, St 20,667 Claims. (Cl. 243-6) This invention relates to pneumatic tube systems, and,

more particularly, vto light-weight pneumatic tube systems having extensive drive tube routes.

' Two blowers are usually provided for dispatching carriers over long drive tube routes. One blows air in at one end of the tube and the other draws air out at the opposite end. The longer the tube, the more powerful are the blowers required. The use of extremely powerful blowers produces undesirable pressure conditions in the drive tubes and connected equipment. This is particularly true of the dispatch or receiving stations since it makes opening of the stations very difficult, and, in some cases, completely unsuitable for manual operations. In some cases, the high pressure may force the station doors open or even burst light-weight stations.

It is known to eliminate these problems by subdividing a long route into shorter lengths'which are interconnected by locks. For instance, it is taught in US. patent application Serial No. 195,604, now Patent No. 3,148,845, to use a reversible blower associated with each lock to draw carriers to the lock and through the entrance flap associated with it. As this point, the blower is reversed to apply compressed air behind the carrier to force it along the next section of tubing. An entrance and an exit flap are required for each lock section. When a carrier enters a lock section, the entrance flap closes and the exit flap opens so that the reversed flow of air is now behind the carrier.

It is an object of this invention to provide a pneumatic tube system utilizing long drive tubes and intermediate blowers for moving the carriers through the drive tubes which does not require the provision of air-tight seals or drive flaps to separate the blowers.

A feature of our invention is the provision of a pneumatic tube system which is simple in design, inexpensive, requires little maintenance and is safe in operation. This is accomplished by the use of intermediate blowers which subdivide the route into two or several partial routes of approximately equal length. The blowers are reversible and are controlled by contacts positioned in'the drive I tube and operated by the carriers themselves.

Another feature of our invention is the use of two blowers, one at each end of a forwarding tube, which together produce a desirable pressure gradient in the tube, but do not provide enough air velocity to move carriers through the tube. In combination with these two blowers we provide intermediate reversible blowers which cooperate with the two blowers to provide enough air velocity to :move (carriers through the tube while still maintaining a desirable pressure gradient throughout it.

The above-mentioned and other features and objects of this invention will become more apparent by reference to the following description of embodiments thereof, taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is aschematic diagram'illustrating a pneumatic tube system utilizing one intermediate blower, and the corresponding pressure and air velocity diagrams of the system; and

FIGURE 2 is a schematic diagram illustrating a pneumatic tube system utilizing a plurality of intermediate blowers and the corresponding pressure and air velocity diagrams of the system.

3,265,324 Patented August 9, 1966 ice The drive tube 1 of the pneumatic tube system shown in FIGURE 1 is quite extensive, for example, in the range of 800 meters in length. Blowers are normally provided at each end of tube 1, such as blowers 2 and 3, in order to produce a sufiicient air velocity for moving carriers through tube 1. They would have to produce a pressure gradient curve such as A so that an air velocity A is maintained throughout the length of the tube. The air velocity is constant throughout tube 1 under ideal conditions.

The large pressure differential produced by the use of two blowers with sufiicient strength to produce pressure gradient A is undesirable. The pressure may be too great for stations in a light-weight system to withstand. This problem is solved, in accordance with 'our invention, by providing blowers 2 and 3 which together produce pressure gradient curve B. The combined pressure of blowers 2 and 3 will then result in an air velocity B which is insufiicient to move a carrier through tube 1. The prob lem is that it is now desired to increase the air velocity behind the carrier without substantially increasing the pressure in the tube. This is accomplished, in accordance with our invention, by inserting a third blower 4 intermediate blowers 1 and 2. This blower is reversible and is chosen to be sufficiently wider than blowers 2 and 3 so that when it is aiding blower 2 in moving a carrier from E to F, the flow of air along the tube is always from E to G. That is, the suction created by blower 4 will not overpower blower 3. When blower 4 cooperates with blower 3 to move a carrier from F to G a flow from E to G will still be maintained through the tube since blower 4 is also not strong enough to overcome blower 2.

The effect of blower 2 on the system can now be appreciated by noting the pressure and air velocity diagrams. When a carrier is inserted in station 5 and is to be sent to station 6, blowers 2, 3 and 4 initially cooperate to move the carrier toward F. Blower 2 produces compression while blowers 3 and 4 produce suction. The combined effect of blowers 2, 3 and 4 can now be seen by noting pressure gradient curve C. It can be seen that the pressure gradient from E to F is almost as steep as pressure gradient A resulting in anair velocity (note curve C) along E to F which is sufficient to move a carrier. Of particular interest, it is to be noted that neither the air velocity nor the pressure gradient is constant throughout the length of the tube. Note that the portion of the tube F, G has a much slower air velocity and much more level pressure gradient than the portion E, F.

When a carrier passes the input of blower 4 it trips a sensor 7 which causes control means 20 to reverse blower 4 thereby producing pressure gradient curve D which is approximately parallel to pressure gradient A along portion F, G of tube 1. It is to be noted that the air velocity and pressure gradient are again 'not constant throughout the tube. Both are now greater through portion F, G in order to move the carrier to station 6. By utilizing an arrangement in' accordance with our invention, the overall pressure in the tube is increased very slightly over the overall pressure difference B while producing a sufficient air velocity in the tube-to move carriers through it. 'It often happens that standard blowers are of too great strength for use in particular systems. A system in accordance with our invention can use such standard blowers by providing an air bypass 8 for each blower. The air bypass is merely an aperture leading to the atmosphere and is preferably adjustable. The size of the aperture is determined by the pneumatic strength desired from the blower with which it is associated. Thus, blower 2 produces, in cooperation with its air bypass 8, a desired pressure at point K which is the equivalent pressure that would be produced by a blower having the power needed at that point in the system. Blower 4 in cooperation with its .air bypass 8 produces the pressure or suction which meets the conditions noted above for the intermediate blower with which it is associated. Thus, blower 2 proenough to over-come either the combined effect of blower 2 and its-air bypass or blower 3 and its air bypass while it is strong enough to produce in combination with blowers 2 and 3 and their respective bypasses 8 the air velocity required to move carriers through the tube.

The reversal of air of the intermediate blower can be achieved through control valves, reversing the direction of the fans, or by alternately switching in a suction. or compressed air blower. Our invention is particularly useful in smaller type pneumatic tube systems having small diameter tubes and light carriers. When these systems are to be operated in either direction, blowers 2 and 3 must also be reversible. Circuitry for controlling the direction of operation of blowers 2 and 3 is obvious and is indicated by connecting links 17 and 18 respectively in FIGURE 1. These controls may be operated by push-buttons (not shown) at each station. It can be seen that the change from one-way operation to twoway operation is extremely simple with our system as the only other requirement is that sensor 7 sense carriers travelingin either direction, and such sensors are com.- monly known.

Referring to FIGURE 2, there is illustrated a system utilizing a plurality of intermediate blowers in accordance with our invention. Blowers 10, 11, 12, 13 and 14 are all connected into a long forwarding tube 9. At the time when carrier 15 is in the position shown, blowers 10 and 11 are producing compression while blowers 12, 13 and 14 are producing suction. The combined blowers produce pressure gradient curve H and air velocity curve H. It is to be noted that the pressure gradient and air velocity are much greater in section L, M through which the carrier is passing. When the carrier reaches section M, N it will have tripped the sensor 16 associated with iblower 12 to operate control means 19 associated with blower 12 for reversing blower 12. As can be gathered from the way in which the pressure and air velocity diagrams are shown for the carrier in section L, M, the steep pressure gradient and greater air velocity will next be present in section M, N. Thus, our system effectively moves the increased air velocity and increased pressure gradient along with carrier '15. In this manner a large pressure gradient and high air velocity need not be maintained throughout the tube, butonly along the sections where the carrier is being transported.

Curves I and I' represent the conditions which would be present in the tube if only blowers 10 and 14 are used. Air velocity G would be insufiicient to move a carrier through thetube. With our system, air velocity is greatly increased while only slightly increasing the overall pressure present throughout the tube itself.

While we have described the principles of our invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of our invention as set forth in the accompanying claims.

We claim:

1. A reversible pneumatic tube system comprising:

(a) a forwarding tube;

(b) a first'reversible blower connected to a first end of said forwarding tube;

(c) a second reversible blower connected to the opposite end of said forwarding tube, said first and second reversible blowers producing an air velocity which is in itself insuflicient to move a carrier along said forwarding tube;

(d) a reversible intermediate blower connected to said forwarding tube between the respective connections of said first and second reversible blowers to said forwarding tube; and 7 ate blower to cooperate with said first and second reversible blowers to produce an air velocity in a first portion of said forwarding tube of sufficient velocity to move a carrier along said first portion of said tube.

2. A system according to claim 1 further comprising at least one air bypass means, each said air bypass means cooperating with one of said first, second or intermediate reversible blowers to provide a pneumatic source of a de sired pressure.

3. A system according to claim 1, wherein said forwarding tube is free of obstructions to the air flow.

4. A system according to claim 1, wherein said control means further comprises means for causing said intermediate blower to cooperate with said first and second reversible blowers to produce said sufficient air velocity along a second portion of said tube.

5. A system according to claim 4, further comprising a sensor for sensing the passage of carriers past the connection of said intermediate blower to said forwarding tube.

6. A system according to claim 5, wherein said first portion comprises the portion of said forwarding tube between said first reversible blower and said intermediate blower and said second portion comprises the portion of said forwarding tube between said second reversible blower and said intermediate blower.

7. A reversible pneumatic tube system comprising:

(a) a forwarding tube;

(b) a first reversible blower connected to a of said forwarding tube;

(c) a second reversible blower connected to the opposide end of said forwarding tube, said first and second reversible blowers producing an air velocity which is in itself insufficient to move a carrier along said forwarding tube;

I (d) a plurality of reversible intermediate blowers connected to said forwarding tube between the respective connections of said first and second reversible blowers to said forwarding tube; and

(e) control means for causing said intermediate blowers to cooperate with said firstand second reversible blowers to provide an air velocity in a desired one of a plurality ofpredetermined portions of said forwarding tube which is sufiicient to move a carrier through said desired portion.

8. A system according to claim 7, wherein said predetermined portions are the portions of said forwarding tube between respective pairs of adjacent blowers.

9. A system according to claim 7 further comprising at least one air bypass means, each said bypass means cooperating with one of said blowers to provide a pneumatic source of a desired pressure.

10. A system according to claim 7 further comprising a plurality of sensors, one said sensor being associated with each of said intermediate blowers for detecting when a carrier passes the connection of said intermediate blower to said forwarding tube.

References Cited by the Examiner UNITED STATES PATENTS 623,509 4/1899 Bostedo 243-6 2,763,446 10/1956 Hanson 2437 (e) control means for causing said reversible intermedi- 

1. A REVERSIBLE PNEUMATIC TUBE SYSTEM COMPRISING: (A) A FORWARDING TUBE; (B) A FIRST REVERSIBLE BLOWER CONNECTED TO A FIRST END FOR SAID FORWARDING TUBE; (C) A SECOND REVERSIBLE BLOWER CONNECTED TO THE OPPOSITE END OF SAID FORWARDING TUBE, SAID FIRST AND SECOND REVERSIBLE BLOWERS PRODUCING AN AIR VELOCITY WHICH IS IN ITSELF INSUFFICIENT TO MOVE A CARRIER ALONG SAID FORWARDING TUBE; (D) A REVERSIBLE INTERMEDIATE BLOWER CONNECTED TO SAID FORWARDING TUBE BETWEEN THE RESPECTIVE CONNECTIONS OF SAID FIRST AND SECOND REVERSIBLE BLOWERS TO SAID FORWARDING TUBE; AND (E) CONTROL MEANS FOR CAUSING SAID REVERSIBLE INTERMEDIATE BLOWER TO COOPERATE WITH SAID FIRST AND SECOND REVERSIBLE BLOWERS TO PRODUCE AN AIR VELOCITY IN A FIRST PORTION OF SAID FORWARDING TUBE OF SUFFICIENT VELOCITY TO MOVE A CARRIER ALONG SAID FIRST PORTION OF SAID TUBE. 